Food allergy (FA) is now a major public health concern. Food allergy is both common?affecting ~8% of US children?and costly?resulting in ~$24.8 billion dollars per year in expenditures by the healthcare system and U.S. families. Approximately 40% of children with food allergy have experienced a severe, life-threatening allergic reaction, and 30% report allergies to multiple foods. Few studies have been conducted to track FA-specific T cells over time using epitopes and tetramer technology during the course of OIT. We hypothesize that distinctive patterns of T cell responses occur throughout OIT to shrimp or milk or cashew, and these can be revealed by immunophenotyping of cells responding to specific epitopes, including RNA-Seq assays, ATAC-Seq assays and TCR repertoire analyses. The results of the proposed studies will enable the production of useful tools for T cell reagents for shrimp, milk, and cashew allergens. Moreover, if the study aims are met, we will be able to further our knowledge of natural tolerance vs persistence vs treatment responsive vs treatment refractory shrimp, milk, or cashew allergy. Building upon our previous research in OIT, we propose a single clinical study to obtain fresh blood samples to optimize T cell reagent discovery and validation and, simultaneously, test the T cell reagent tools for their diagnostic, prognostic, and mechanistic use in food allergic patients before, during, and after OIT. Furthermore, we will identify, characterize, and validate new T cell epitopes for important food allergens not previously examined, such as milk, cashew, and shrimp. We will focus on epitope identification and validation, track the numbers and functions of epitope-specific T cells during stages of food allergy OIT, and then associate these parameters with careful phenotypic and endotypic characterizations in food allergic individuals. Our overall objectives are to conduct groundbreaking research in the areas of allergen epitope-specific T cell reagent identification and application to understanding mechanisms of food allergy. To advance these objectives, the PI(Nadeau) will work with Drs. Pulendran,Chang,Davis,Elias,Chinthrajah,Maecker, Andorf, and Desai.